The present invention relates to a transmission for a vehicle, which is provided with a heat exchanger for exchanging heat between oil supplied to a given location inside a transmission case and a heat transfer medium (heat medium) supplied from outside of the transmission case. The present invention also relates to a method of manufacturing the transmission.
Automatic transmissions mounted on vehicles are provided with a transmission mechanism having hydraulic actuators, such as for a clutch and a brake, and the gear is suitably changed according to the operating state of the vehicle by controlling supply and discharge of hydraulic oil to/from the hydraulic actuators. On the other hand, manual transmissions are provided with a transmission mechanism having a pair of parallel shafts and a plurality of gear trains which bridge between the shafts, and a desired gear ratio is selected by using one of the gear trains in a power transmitting state in response to an operation of a gear stick.
As for both the automatic and manual transmissions, oil is suitably supplied to gear mating parts and bearings for lubrication and cooling, and, particularly for the automatic transmission, oil is also supplied and discharged to/from hydraulic chambers of the hydraulic actuators and a torque converter.
If the temperature of the oil supplied to each component inside a transmission case is too low, the viscosity of the oil becomes high, and thus, inconveniences occur, such as a delay in the hydraulic control, and an increase in the rotational resistance of the rotating bodies (e.g., gears). On the other hand, if the temperature of the oil is too high, inconveniences occur, such as a faster deterioration of the oil. Thus, in order to cool or heat the oil supplied to each component inside the transmission case to a suitable temperature, heat exchangers are conventionally used for exchanging heat between the oil and heat medium, such as water, supplied from, for example, a cooling system of an engine, which is located outside the transmission case.
For example, as disclosed in JP2014-149017A, a conventional heat exchanger used in a transmission is attached to a perimeter surface of a transmission case. Oil supplied to an oil channel formed in the heat exchanger is cooled down to a suitable temperature by a heat exchange with a low-temperature heat medium supplied from an engine cooling system etc., or heated by a heat exchange with a high-temperature heat medium, and is then supplied to each component inside the transmission case.
However, since the conventional structure in which the heat exchanger is attached outside the transmission case disclosed in JP2014-149017A increases the transmission in size, an improvement may be possible in the way to mount the transmission on the vehicle.
In addition, since it is necessary to avoid interference of peripheral components of the transmission with the heat exchanger attached outside the transmission case and piping connected to the heat exchanger, a degree of freedom in layout of the peripheral components is reduced.
In addition, brackets, and seal members for preventing an oil leakage, etc., are required in order to attach the heat exchanger to the outside of the transmission case, and thus, there are problems such that the number of components increases and the assembly becomes complicated.